The primary aim of this research project is to examine the attenuation characteristics of hearing protectors at low and high sound intensities. The present American standard (ANSI S3.19-1974) for the evaluation of hearing protectors advocates use of a procedure utilizing threshold-level signals. Considerable evidence suggests that attenuation measured at low intensities (threshold levels) over-estimates the protection provided at high sound intensities. A method of assessing real-ear protection at low and high intensities, therefore, is needed. Several of the methods employed previously to measure the attenuation characteristics of hearing protectors at low and high sound levels, however, appear to be confounded by extraneous variables. Consequently, several new methods of assessing hearing protectors in low and high levels of noise are being examined here. The second aim of the proposed project is to evaluate the stability of hearing protectors. That is, the question asked for this phase of the project is how do the attenuation characteristics of hearing protectors (specifically, earplugs) change over time following repeated use? This issue is of considerable practical importance to the overall effectiveness of personal hearing protection as a viable hearing conservation strategy.